Ovarian biochemical changes associated with chronological aging will be sought as signals for physiological change. In vitro steroidogenesis, 20 alpha hydroxysteroid dehydrogenase activity, and cholesterol metabolism will be measured in rat ovaries. Associated changes in plasma progesterone, estradiol and testosterone will be assessed as well as the ovarian response to gonadotrophin. The potential of an induced hormonal imbalance during neonatal maturation of premature physiological ovarian aging will be examined.